1. Field of the Invention
The invention relates to a frictional feeder for paper stacks or the like, comprising a frictional conveyor belt below the paper stack and a curved support on which the paper sheets of the stack rest with their rearward end and which is adjustable with respect to its slant relative to the plane of the paper sheets.
2. Description of the Related Art
Such frictional feeders are comprised of a frictional component group and a conveying component group. The frictional component group includes the frictional conveyor belt and the curved support. The curved support guides the paper sheets or similar products of the stack in cooperation with a forward curved guide into the product passage which transfers the individual paper sheets onto the conveying component group. The curved support receives a portion of the weight of the paper sheets and reduces the pressure of the paper sheets acting on the frictional conveyor belt. This is important with respect to a disturbance-free operation of the frictional feeder. Small changes or errors when adjusting the slant of the curved support can result in malfunction of the feeder.
It is already known to adjust the slant and the spacing to the plane of the frictional conveyor belt.
It is an object of the present invention to provide a frictional feeder of the aforementioned kind in which the slant of the curved support can be adjusted in a reproducible manner, independent of the force acting on the curved support, and with which a fine adjustment is possible without requiring an additional fixation of the curved support after completion of the adjusting operation.
In accordance with the present invention, this is achieved in that an elbow lever is fastened to the curved support and that the elbow lever is pivotable by means of a self-locking drive unit for the purpose of adjusting the slant of the curved support.
According to the invention an elbow lever is provided with which the curved support is connected to the self-locking drive unit. The self-locking drive unit allows an adjustment of the slant without running the risk that this adjustment, once it has been undertaken, is again changed, for example, by the weight of the paper sheets of the stack.
In an especially advantageous manner, the self-locking drive unit is comprised of a spindle drive comprising a spindle and a spindle nut. The required self-locking action is realized by providing a correspondingly minimal pitch of the thread of the spindle.
According to another preferred embodiment, the end of the elbow lever which is not acting as a support of the spindle nut, is pivotably supported on a lever arm which is also pivotably supported for adjusting the slant of the curved support.
Preferably, the stationary bearing location of the spindle is located on the pivot axis of the lever arm.
Advantageously, the curved support together with the drive unit and the bearing locations can be adjusted in the direction of the axis of the spindle. When the frictional feeder is configured in this way, a further adjusting possibility is provided in order to adjust not only the slant of the curved support but also the height of the curved support relative to the paper stack.